Perfluorinated polyether compounds are widely used as e.g. a lubricant, a surface modifier or a surfactant. For example, as a compound having its terminal group converted to —CH2OH, a compound represented by the following formula (I)(wherein each of h and i is an integer of at least 1) has been known (for example, Non-Patent Document 1):HO—CH2CF2O—(CF2CF2O)h—(CF2O)i—CF2CH2OH   (I)
It is known by the document that the surface having a coating film formed by application of the compound (I) on the substrate surface, has a nature (self-replenishing property) such that when a part of the coating film becomes defective, the compound (I) around the defective portion will cover the defective portion to replenish the defective portion. Further, it is known that a —CH2OH group present at the molecular terminal of the compound (I) is involved in such self-replenishing property.
As a perfluorinated polyether compound such as the compound (I) has become to be used under a high temperature condition, a compound having a lower vapor pressure has been desired. In an attempt to accomplish a low vapor pressure, it has been attempted to increase the molecular weight, but when it is attempted to increase the molecular weight of the compound (I), there has been a problem that the viscosity increases remarkably, whereby its application tends to be difficult. Further, there has been a problem that the proportion of —CH2OH groups per unit volume becomes low by the increase of the molecular weight, whereby the self-replenishing property tends to deteriorate.
As a compound to solve such problems, a compound represented by the following formula (II) has also been proposed (in the following formula, each of h and i is an integer of at least 1), but also has a problem that the viscosity is high:HO—CH2CH(OH)CF2O—(CF2CF2O)h—(CF2O)i—CF2CH(OH)CH2—OH   (II)
Further, each of the compound (I) and the compound (II) requires a —OCF2O— unit in its molecular structure. This unit is a unit which causes the decomposition reaction of the compound, and thus the compound having such a unit has had a problem that it undergoes deterioration in its use (e.g. Non-Patent Documents 2, 3 and 4).
As a perfluorinated polyether compound having no —OCF2O— unit, a compound wherein terminals are —COOH groups, has been reported (e.g. Non-Patent Document 5). However, such a compound wherein the terminals are —COOH groups, has had a problem that when left under a high temperature condition, —COOH terminals undergo CO2 removal, whereby polar terminal groups will be lost, and the self-replenishing property will deteriorate. Further, the compound having —COOH groups has had a problem that the acidity of —COOH groups is large, thus causing corrosion.
Non-Patent Document 1: C. Tonelli et al, J. Fluorine Chem., Vol. 95, 1999, p. 51-70
Non-Patent Document 2: W. Fong et al “IEEE Transactions on Magnetics”, vol. 35, No. 2, March 1999, p. 911-912
Non-Patent Document 3: J. Scheirs, “Modern Fluoropolymers”, John Wiley & Sons Ltd., 1997, p. 466-468
Non-Patent Document 4: P. H. Kasai, “Macromolecules”, Vol. 25, 1992, p. 6791
Non-Patent Document 5: Kyle W. Fellling et al, J. Fluorine Chem., Vol. 125, 2004, p. 749-754